Hey there! Sign in to join this conversationNew here? Join for free
    • Thread Starter
    Offline

    2
    ReputationRep:
    why is it that caesium chloride shows the largest deviation in the group I chlorides from theoretical and born haber lattice formation enthalpies? They only reason why it would show a difference is because it shows a covalent character but it has the largest cation radius out of the group I chlorides and has the same charge so the charge density is less...help?
    Offline

    11
    ReputationRep:
    (Original post by smetin92)
    why is it that caesium chloride shows the largest deviation in the group I chlorides from theoretical and born haber lattice formation enthalpies? They only reason why it would show a difference is because it shows a covalent character but it has the largest cation radius out of the group I chlorides and has the same charge so the charge density is less...help?
    Look up Fajan's rule, dealing with polarisability and covalency.
    • Community Assistant
    • Study Helper
    Offline

    15
    ReputationRep:
    Community Assistant
    Study Helper
    (Original post by smetin92)
    why is it that caesium chloride shows the largest deviation in the group I chlorides from theoretical and born haber lattice formation enthalpies? They only reason why it would show a difference is because it shows a covalent character but it has the largest cation radius out of the group I chlorides and has the same charge so the charge density is less...help?
    Indeed according to the conventional theory CsCl should be a pure ionic solid giving good agreement between BH and electrostatic theory.

    I would suggest that the deviation is (possibly) a result of the different crystal structure of CsCl.

    The two ions are roughly the same size so the crystal structure adopted is a primitive cubic lattice, whereas the chlorides of all of the other alkali metals have the sodium chloride face centre cubic structure.

    Don't quote me on this though, as I'm just looking at ideas and have not thought this through.
 
 
 
Poll
Do you agree with the PM's proposal to cut tuition fees for some courses?

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.